Writing Algebraic Expressions

Writing algebraic expressions can be confusing for some. Use this lesson on writing algebraic equations to help you better understand them.

Writing multi-part algebraic expressions

Some expressions are slightly more complicated than the ones we looked at on the last page. For instance, some expressions include more than one math operation. Take this one as an example:

Five times the sum of four and two

If you were to translate this word for word, you'd change the word times to a multiplication symbol () and put a plus sign (+) between the four and the two. Your expression would look like this:

5 4 + 2

However, this wouldn't get us the right answer. This is because the order of operations would call for you to multiply 5 times 4 first, then add 2. However, our written expression asks us to multiply 5 by the sum of 4 and 2. In other words, we need to add 4 and 2 first, then multiply that number by 5.

If you're familiar with algebraic notation, you know that parentheses are useful in cases like this—they let you group part of an expression and solve it separately from the rest. Here, we can use them to group 4 and 2—the numbers being added.

5 ⋅ (4 + 2)

This is the correct way to write the expression. Based on the order of operations, always solve operations in parentheses first. Here, you'd add 4 + 2, then multiply that sum by 5—in other words, exactly what was written in the original expression.

Watch this video from Khan Academy to see more examples of algebraic expressions with more than one operation:

Assessment

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